Yes when there are many players near then it uses a codec that takes less bandwidth (300 bytes per second for each listener) which is still good quality when it is plain human voice (and the microphone is good). For good quality music transmission it would probably be better to do internet radio (and put an npc in a graal level which plays the url
The latest Graal version (v2.14 revision4) that was uploaded yesterday should fix all voice chat crashing problems, got no error report of that version yet.